There are a number of industrial applications which involve the application of air or another gas to a liquid. For example, in the treatment of wastewater, it is common practice to utilize aeration/mixing equipment to aerate and mix the wastewater in order to promote the biological processes that are involved in the treatment. Diffused aeration makes use of submerged diffusers which are supplied with air by a piping network and which discharge the air into the liquid. Both coarse bubble and fine bubble diffusers are used. The air discharging from the diffusers serves both to aerate the liquid in the treatment basin and to effect the necessary mixing of the liquid. The air supply piping network can be arranged in a variety of different ways. For example, the air supply pipes can be situated at a submerged location in one type of system. In another type of system, the main air supply pipes float on top of the liquid, and submerged diffuser assemblies are connected with the floating pipes by tubing or hoses. The diffuser assemblies can either be suspended from the floating pipe at a location above the floor of the basin or located on the basin floor. In either case, each diffuser assembly must be held down in the basin to counteract its buoyancy when filled with air.
Typically, ballast that is used to hold down the diffusers takes the form of a concrete or metal block which must be heavy enough to overcome the buoyancy of the diffuser assembly when it is filled with air. Recognizing that the diffuser assembly may include multiple diffusers each presenting a considerable volume which is filled with air, it can be appreciated that the ballast blocks must be rather large and heavy. This may make the diffuser assemblies difficult to handle and to install. Installation is particularly difficult in deep basins and in applications which involve high energy systems requiring the diffusers to be placed closely together. Diffuser assemblies that are suspended may also be difficult to stabilize and prevent from moving excessively due to the forces that result from the discharge of air from the diffusers.